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This may interest some.
What is being displayed in that video I'm pretty sure is not cavitation. It is just aerated water from turbulence. If you feed aerated water into a pump it will never pump efficiently.

I was impressed by the sheer volume of water that was being moved about though.
 

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What is being displayed in that video I'm pretty sure is not cavitation. It is just aerated water from turbulence. If you feed aerated water into a pump it will never pump efficiently.

I was impressed by the sheer volume of water that was being moved about though.
There's another video where the impellor was swapped out to his one with zero other changes and all those bubbles were virtually gone, so read into that what you will. I really have no idea, I just found the video and thought you guys might like to see it.
 

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nissan patrol
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This may interest some.


For those that don't know this is Derk John Brocx water pump tester.

This illustrates what cavitation looks like in an engine, but unfortunately as a pump tester it misses a few critical elements.

Firstly, it does not run a timing cover, so the critical gap between impeller and timing cover radius cannot be optimised.
He uses a straight bit of steel which can be used on multiple pumps making it some what universal.

Secondly, there is no engine.
No block, No head. No water galleries.
The water jug is set to simulate the engine.

Thirdly, there is no heat in the system.
Water and cavitation behave ALOT differently when water is over 85°c.

Then there is the associated plumbing, but at this point it doesn't really matter.
 

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GQ Dual Cab. TD42Ti with fruit.
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Looks like a timing cover is used to me. His steel plate is to replicate the steel plate behind the timing case.

Volume will be effected greatly from having no restrictions at all in the system as Plumma says. But it sure looks like it would make a good washing machine.
 

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2003 GUIII - TD27T
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You need to look at the radiator, bottom hose and thermostat as one. The radiator feeds the bottom hose which feeds the lower thermostat housing. This goes right past the bypass, so distance or length is not a consideration. The bypass hole is approximately 18mm while the radiator supply is over 40mm. Then there is the head pressure of the radiator being higher than the bypass, which if you remove the upper thermostat housing and thermostat, the water will gizer out of bypass hole until the level of the radiator matches the bypass level.
Then with the bypass, is it anything but a nice transition of passage for the water from out of the head around the thermostat around corner to a hole with poor radius and transition.

Using pressure and vacuum gauges on the system with standard bypass and plumbing, a drop in pressure is noted on thermostat opening. Less resistant =Less pressure.
Pressure loss is directly proportional to hose length. period,
there are formulas out there to work this stuff out.

Head pressure of a radiator has nothing to do with a bypass,
The bypass is on the suction side of the pump,
there will be no head pressure from the radiator affecting it under running conditions,

Unless you think any head pressure in the radiator
can overcome the flow from the thermostat to the radiator?

Where was this measured a drop in pressure noted on thermostat opening?
because the laws of physics are pretty clear that a drop in pressure,
with a lengthed path for the water,
would indicate that resistance has increased.

Showing that that radiator is indeed a path of greater resistance over the bypass.
 

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nissan patrol
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Pressure loss is directly proportional to hose length. period,
there are formulas out there to work this stuff out.

Head pressure of a radiator has nothing to do with a bypass,
The bypass is on the suction side of the pump,
there will be no head pressure from the radiator affecting it under running conditions,

Unless you think any head pressure in the radiator
can overcome the flow from the thermostat to the radiator?

Where was this measured a drop in pressure noted on thermostat opening?
because the laws of physics are pretty clear that a drop in pressure,
with a lengthed path for the water,
would indicate that resistance has increased.

Showing that that radiator is indeed a path of greater resistance over the bypass.

I feel as no matter how I explain it you will disagree. That's fine, we'll have to agree to disagree.

But can you explain to me, why is it when the thermostat opens, albeit even as little as 1mm, it sends water through this gap through the radiator.

Wouldn't the water take the easier path through the open hole of the bypass??
 

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nissan patrol
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I don't really know what you think you're explaining
when all you do is contradict yourself all the time?

These are the comments to why I don't want anything to do with this thread.

....But I look forward to your research and devolpment on the subject .
 

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But can you explain to me, why is it when the thermostat opens, albeit even as little as 1mm, it sends water through this gap through the radiator.

Wouldn't the water take the easier path through the open hole of the bypass??
Because water is already flowing through the bypass at capacity,
because it is indeed the path of least resistance.
The video Kiwi_dingo put up shows the volume the pump is capable of.
Once a route is saturated/at capacity the next easiest path
or in this case the only other path will take the overflow/excess.

You can only get so much flow through any hose until it reaches capacity
and then resistance then increases.

Water flowing through the radiator when the thermostat opens as little as 1mm
doesn't prove nor show that the radiator is the path of least resisitance.

Perhaps i should have been clearer with my earlier statements/hypothesis
but i thought you had a basic grasp of fluid dynamics.

I have already proved to myself and stated so earlier in this thread
that cavition or aeration if you prefer increases when the bypass fully closes
and all coolant is sent throught the radiator.

Leading me to believe, along with basic physics,
that the longer path through the radiator will increase fluid drag/resistance
and the suction of the pump aerates the coolant even more
and then it's all downhill for the cooling systems ability to hold temps under control.

However keep the bypass open which in turn reduces cavitation/aeration on the suction side of the pump and it's all happy sailing.

Again, this is just what i've proven with my setup.

Another hint is that early on is this thread people where reporting greater temperature control
with hotter thermostats.

When you consider the wax pellet thermostat is linear in operation with regards to temperature,
it can only mean that the later or hotter a thermostat opens will also mean a hotter/later tempature that the thermostat is fully open, which also means a later fully closed bypass.

Again since an open bypass allows the pump to pump more efficiently with less aeration/cavition,
higher stable temperatures are reached before the cooling system can't hold on and runs away.

Please discuss.
 

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nissan patrol
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Because water is already flowing through the bypass at capacity,
because it is indeed the path of least resistance.
The video Kiwi_dingo put up shows the volume the pump is capable of.
Once a route is saturated/at capacity the next easiest path
or in this case the only other path will take the overflow/excess.

You can only get so much flow through any hose until it reaches capacity
and then resistance then increases.

Water flowing through the radiator when the bypass opens as little as 1mm
doesn't prove nor show that the radiator is the path of least resisitance.

Perhaps i should have been clearer with my earlier statements/hypothesis
but i thought you had a basic grasp of fluid dynamics.

I have already proved to myself and stated so earlier in this thread
that cavition or aeration if you prefer increases when the bypass fully closes
and all coolant is sent throught the radiator.

Leading me to believe, along with basic physics,
that the longer path through the radiator will increase fluid drag/resistance
and the suction of the pump aerates the coolant even more
and then it's all downhill for the cooling systems ability to hold temps under control.

However keep the bypass open which in turn reduces cavitation/aeration on the suction side of the pump and it's all happy sailing.

Again, this is just what i've proven with my setup.

Another hint is that early on is this thread people where reporting greater temperature control
with hotter thermostats.

When you consider the wax pellet thermostat is linear in operation with regards to temperature,
it can only mean that the later or hotter a thermostat opens will also mean a hotter/later tempature that the thermostat is fully open, which also means a later fully closed bypass.

Again since an open bypass allows the pump to pump more efficiently with less aeration/cavition,
higher stable temperatures are reached before the cooling system can't hold on and runs away.

Please discuss.

There's alot here to discuss.

Firstly I'll just put forward that the majority of our cooling system devolpment is finished.
We are now just in final testing stage through summer making sure the system behaves.
And we are now running a 12mm fuel pump, although not at 'full' tune, it is by far the most power the engine has ever made and is no slouch.

But the first step which we took, is to produce a pump that does not cavitate. This involves pump design and associated plumbing.

The rest is irrelevant if you can't sort the pump.


No I'll be completely honest, I would be surprised if anybody could achieve this.
All the pumps available for the td42 cavitate.
Some are close, others are not even in the ball park.

I was lucky enough to be able to have access to people who have been solving cooling issues and modifying pumps with decades of experience Even with this knowledge, it took about 4 different pump incarnations and about 6 months testing to eradicate cavitation.

That's when the fun begins...
 

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There's alot here to discuss.

The rest is irrelevant if you can't sort the pump.
You didn't discuss anything about what i posted,
just rambled on about stuff other people have done for you.

The rest is not irrelevant if it's causing aeration
or at its extreme, cavitation at the pump.
 

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You didn't discuss anything about what i posted,
just rambled on about stuff other people have done for you.

The rest is not irrelevant if it's causing aeration
or at its extreme, cavitation at the pump.

From what I've read most of what you talk about is theory with no testing.

How did you test the maximum flow of the bypass?
Was the bypass like kiwi dingo' s video?
Half full of bubbles.
Just removing the bubbles would increase water volume.
How have you checked for cavitation??
How have you measures pump efficiency?
 

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How did you test the maximum flow of the bypass?
How would you test this? and more to the point why do you need to test this? It's a hole mere inches from the suction side of the pump, if the bypass is open there will be the maximum flow allowable due to the size of the aperature and the fact it's the path of least resistance till it reaches capacity of course, the bypass isn't capable of flowing all the pump can move.

Was the bypass like kiwi dingo' s video?
Half full of bubbles.
Sorry don't have x-ray vision,
But since getting my cooling system to the point, where the bypass is always open at least a little bit
and this has prevented the cooling system running away uncontrollably when pushed hard,
I'm going to say no.


Just removing the bubbles would increase water volume.
Physics 101

How have you checked for cavitation??
No pitting on the front timing cover,
it's alloy and the closest to the source and most susceptible to pitting.


How have you measures pump efficiency?
It holds temps stable towing 3 ton, i'd say it works ok.

P.S. This just shows you only read what you want to read,
i've stated this stuff before earlier in this thread,
but it doesn't conform to your viewpoint so you discard it.
 

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How did you test the maximum flow of the bypass?
How would you test this? and more to the point why do you need to test this? It's a hole mere inches from the suction side of the pump, if the bypass is open there will be the maximum flow allowable due to the size of the aperature and the fact it's the path of least resistance till it reaches capacity of course, the bypass isn't capable of flowing all the pump can move.

Was the bypass like kiwi dingo' s video?
Half full of bubbles.
Sorry don't have x-ray vision,
But since getting my cooling system to the point, where the bypass is always open at least a little bit
and this has prevented the cooling system running away uncontrollably when pushed hard,
I'm going to say no.


Just removing the bubbles would increase water volume.
Physics 101

How have you checked for cavitation??
No pitting on the front timing cover,
it's alloy and the closest to the source and most susceptible to pitting.


How have you measures pump efficiency?
It holds temps stable towing 3 ton, i'd say it works ok.

P.S. This just shows you only read what you want to read,
i've stated this stuff before earlier in this thread,
but it doesn't conform to your viewpoint so you discard it.

No, I'm just not going to waste time searching back through the thread.

Checking for cavitation damage....

Is not checking cavitation.
You can do a simple funnel test at idle speeds or you can use as we do scientific glassware. This give you are visual on water behavior. Otherwise you are guessing.

Bypass can't flow all the pump can move??
I can guarantee that my modified waterpump has more pressure and volume than anything you have, yet works perfectly fine with the thermostat closed. Tested.
Pressure, flow, pump vacuum and cavitation.
All tested and passed with flying colours.

I too don't have x-ray goggles so everthing is visually checked through sight glasses and gauges. NO GUESSING.


And you says holds a stable temp.
How??
If you cannot have the thermostat shut.
The thermostat is what controls the system temp by OPENING and CLOSING.
 

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No, I'm just not going to waste time searching back through the thread.

No, you never read or took onboard or contemplated anything
that I or anyone else wrote that contradicted your beliefs.


Checking for cavitation damage....

Is not checking cavitation.
You can do a simple funnel test at idle speeds or you can use as we do scientific glassware. This give you are visual on water behavior. Otherwise you are guessing.

Bypass can't flow all the pump can move??

Yes, the bypass cannot efficiently move all the coolant,
when the bypass is fully open (thermostat fully closed) pressure in the block will be high.

Pressure is a measurement of resistance to flow, same as boost.

A simple pressure test in the block/head when the thermostat is shut (bypass open)
and another when the thermostat starts to open will confirm this.
Pressure will be high will thermostat is shut (bypass open) and the pressure will drop when the thermostat opens.


I can guarantee that my modified waterpump has more pressure and volume than anything you have, yet works perfectly fine with the thermostat closed. Tested.
Pressure, flow, pump vacuum and cavitation.
All tested and passed with flying colours.

I too don't have x-ray goggles so everthing is visually checked through sight glasses and gauges. NO GUESSING.

I don't have a modified pump, just an off the shelf GMB,
and no it wasn't a guess that when pushed hard
and my temps hit the value that indicates that the thermostat is fully open(bypass fully closed)
and then the engine temp runs away uncontrollably that i have aeration.
It was the collaboration of other members in this thread that lead me to this conclusion
and a few years of experience twisting spanners as a truck mechanic.

Really? What else could it be?
what do you think causes the pump to aerate when the thermostat fully closes?


And you says holds a stable temp.
How??
If you cannot have the thermostat shut.
The thermostat is what controls the system temp by OPENING and CLOSING.

Because for about the umpteeth time,
the bypass being open minimizes pump aeration. (even if it's just open 2-3mm or so)

You don't need or want the thermostat to fully open or fully shut the bypass to control temps.
I've found it's the closing of the bypass when the thermostat is fully open that causes the aeration/cavitation in the pump
due to the longer more restrictive path through the radiator with a standard oem style water pump.

Remember, the thermostat does 2 things at once,
it allows the pump to draw water from the radiator when the thermostat starts to open
and at the same time it also controls the bypass flow.

you seem to think the bypass must be either fully closed or open?

I can assure you in my case, at operating/driving temps, it floats somewhere in the middle,
and i never want it to fully close the bypass because it then causes aeration.

When the thermostat gets to the point that it's fully open (bypass fully closed)
the thermostat has lost control, it's a last ditch effort to bring it back under control.

Unfortunately the oem pump can't manage this situation
and from what i've read, neither can any aftermarket pumps
and this then aerates the coolant and temps skyrocket uncontrollably.

Again just my findings, with help from other posters in this thread
and has lead to me work out why and how i've managed to get a stable cooling system.
 

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nissan patrol
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Yes, the bypass cannot efficiently move all the coolant,
when the bypass is fully open (thermostat fully closed) pressure in the block will be high.

Pressure is a measurement of resistance to flow, same as boost.

A simple pressure test in the block/head when the thermostat is shut (bypass open)
and another when the thermostat starts to open will confirm this.
Pressure will be high will thermostat is shut (bypass open) and the pressure will drop when the thermostat opens.

Pressure in the block is high?

How high?

How much pressure is too much?

Isn't pressure good??
 

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Because for about the umpteeth time,
the bypass being open minimizes pump aeration. (even if it's just open 2-3mm or so)

You don't need or want the thermostat to fully open or fully shut the bypass to control temps.
I've found it's the closing of the bypass when the thermostat is fully open that causes the aeration/cavitation in the pump
due to the longer more restrictive path through the radiator with a standard oem style water pump.

Remember, the thermostat does 2 things at once,
it allows the pump to draw water from the radiator when the thermostat starts to open
and at the same time it also controls the bypass flow.

you seem to think the bypass must be either fully closed or open?

Interested in how you tested this.
We've found the opposite through testing (with a modified pump) that the vacuum created from an undersized bypass is relieved when the thermostat opens.

In regards to thermostat operation, the one thing I don't want is the thermostat to be a FULL open. As you state the thermostat has lost control and only reducing load will reduce temps
 
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